Furnace construction



Aug. 29, 1933. c. E. LEHR FURNACE CONSTRUCT I ON Filed Aug. 22, 1931 4 Sh'e'sfts-Sheet 2 Aug. 29, 1933. c. E. LEHR FURNACE CONSTRUCTION 4 sheets-'sheet 3 Filed Aug. 22, 1951 Aug. 29, 1933. Q E EHR 1,924,936

FURNACE CONSTRUCT ION Filed Aug. 22, 1931 4 Sheets-Sheet 4 ha/'MSE Z elli".

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Patented Aug. 29, 1933 FURNACE CONSTRUCTION Charles E. Lehr, Bethlehem, Pa., assigner to Bethlehem Steel Company, a. corporation of Pennsylvania Application August 22, 1931. Serial No. $58588 10 Claims.

My invention has for its object the improvement in the construction of regenerative chambers of open hearth furnaces, to permit of easy removal and replacement of portions thereof which become clogged with particles precipitated from the gases, and the arrangement of the construction and flow of air and gases so that a more eiiicient and convenient utilization can be made of the excess heat in the outflowing gases beyond that required for preheating purposes. In addition other objects are attained which will be made apparent in the following description. The invention relates more particularly to furnaces Where fuel is admitted through the roof of the furnace and where the outflowing gases leave the furnace at a temperature higher than in the usual practice.

In the accompanying drawings I have shown more or less diagrammatically for purposes of illustration only embodiments of this invention, it being understood that the drawings do not denne the limits of the invention as changes may be made in the construction of different elements without departing from the spirit of the invention.

Fig. 1 is a vertical section through an open hearth furnace and one of its communicating flues and stacks, f

Figs. 2 and 3 are cross sections through the iiue and stack respectively, taken on lines 2-2 and 3 3 of Fig. l.

Figs. 4--6 are sections through a removable unit of checker work forming a portion of the regenerative system.

Fig. 7 is a detail of such removable unit.

' Fig; 8 is a plan, partly in section, of an open hearth furnace and its communicating flues together with a waste heat boiler used in conjunction therewith.

Fig. 9 is an elevation of the stacks and contiguous portions of the apparatus shown in Fig. 8..

In Fig. l, 11 is one of a pair of fiues which communicate with the opposite ends of an open hearth furnace 12. It will be understood that the arrangements and appurtenances associated with each of these flues are identical, and that they are used alternately for the passage of burned and unburned gases respectively, so that the illustration and description of one such unit will apply to both. Flue l1 contains two horizontal checker sections 13 and 14, the latter being of considerable length and of ordinary construction, whilethe former is of special design and construction to facilitate its quick and easy removal and replacement. At its far end flue 11 communicates directly with stack l5 of circular section which is filled for a considerable portion of its height with checker work 16. j

Referring to Figs` 4-6 which illustrate the construction of removable checker section 13, the four closed rectangles of pipe 17 are built into a box-like unit by welded spacers 1S and are provided at the corners with perforated pulling plates 19. Water inlet and outlet pipes 20 and 2l are connected to each of the loops of pipe 17 65 and pass upwards through the arched cover 22 on the upper side of which the various pipes are connected through unions 23 to headers 24 and 25. The latter are, through fiexible couplings connected to water supply and drain.v At the top of each of the loops 17, between the connections to inlet and outlet pipes, an internal diaphragm is welded to cause the circulation of water to pass around the loop.

Metal plates 26, 27, and 23 are laid against the 75 bottom and side portions of the pipe loops and a checker work of highly refractory brick is built up inside as nearly to the tcp of the loops as pos-` sible. The cover 22 is built with an arched construction of silica brick inside the rectangularl metal frame 29. It rests along its edges in a recess in the brickwork of the flue, but is separated from contact with this brickwork by a layer of one half inch of refractoryrsand 31, which prevents fusion. Around the sides of the cover luting material is packed as shown at 32. Fig. 7, a section of the arched brick-work kof the cover taken along one of Ythe vertical pipes, shows the circular recess 34 around each pipe which is packed with luting material.

The unit built up as described ts into a recess 33 of the brickwork of the flue so formed that the bottom, sides and top portions of the loops of pipe are all outside the normal section of thev flue and thus escape direct impingement of the highly heated gases. f v

v When it is desired to replace this unit, unions 23 are rst disconnected fromV pipes 20 and 21, the cover 22 is liftedoif by means of suitable rings 35, the checker unit is hoisted out by means of plates 19, a second unit held in readiness is then lowered into place, the layer of sand ref placed around the edge of recess 30 and the cover lowered over the pipe ends and settled onto its seat. The orices for the pipes and the sides of the cover are then luted, and water connections established. y

Between horizontalv checker section 14 and vertical section 16 a space 38 of empty iiue isinterposed, part of which is directly .underneath the being of only secondary importance.

venience in maintenance with this arrangement vertical checker section. This space acts as a dust chamber to collect dust settling from the gases and droppingfrom the checker section above.

The checker sections in chamber le and in stack 15 provide the major portion of the regenerative system, the stack having about and the horizontal chamber 30% of such checker work. The section of the stack is round and that of the horizontal chamber approximately rectangular. It is necessary touse highly refractory brick in section 13 and checker chamber 14, but brick of lower quality is satisfactory in the stack. A

Numerous decided advantages are present in the operation and behavior of a furnace of this type. It has been observed that the most serious clogging by particles of dirt carried over by the burned gases occurs in the first foot or two of the checkerwork. In an open hearth furnace construction in which the gases from the furnace make their rst passage vertically downward through the checker-chamber, a collection of dirt in the upper layers takes place, but it is difficult to remedy the condition by replacing only these upper layers, since, in removing them, dirt and broken bricks drop down and clog the lower spaces. It is thus usually necessary to remove all of the checkerwork in the chamber, an oper ation which is obviously slow and costly. With the removable unit as shown, however, such a renewal can be carried out in a very short time and does not interfere with the regular operation of the furnace.

The checkerwork in chamber 1li is subjected to a high temperature and also a considerable amount of clogging takes place, but this latter to a much less degree than would be the case in the absence of removable section 13. Easy access to this chamber is obtained. by removal of section 13 and in addition a man hole 35 is pro vided for this purpose. Further it is possible after removal of section 13 to block off the heat of the furnace by installing a temporary bulkhead of any sort as shown by dotted lines 37 and' dirt from. the gases, this having been precipitated' by previous checker sections.V

` The complete system of checkerwork thus consists of three separate portions each distinct in' their functions and operation. That in the stack may be considered permanent, and serves the function merely of heat storage and transfer. That in the horizontal chamber is readily accessible for renewal and may be renewed at the end of every campaign or may merely be cleaned and thus last for several campaigns. Its function is both for heat storage and transfer and to precipitate thoroughly thc dust in the'gases. That in the removable section which may be replaced at the end of a campaign or several times during the campaign, serves to precipitate the major portion of the flue dust, and thus protect section 14, its heat storage and transfer function The conis obvious and in addition it produces a substantial saving in labor and the cost of refractoriesj Figs. 8 and 9 show the arrangement-of furnace and lues in which the principles described above.

are embodied in combination with a waste heat boiler for the eflicient utilization of the excess heat of the gases. In these figures 101 and 101' are flues communicating with ports at the ends of the open hearth furnace 102. In the illustration the air is caused to enter the furnace through flue 101 and the burnt gases to leave through similar flue 101', but the flow may be reversed by the operation of suitable dampers which are shown in the illustration and will be more fully described. Part of the burnt gases in 101 passes through the removable checker section 103' and another part is conducted through the by-pass 164', the additionalchecker section 105' of removable construction` such as shown in Figs. 4-7, the fire tube boiler 106, the duct 107 and into header 108. Into this header outside air is also admitted through the intake pipe 109 and the mixture drawn out by the fan 110 and forced through nozzle 111 and throat 112 to the stack 113. The main portion of the gas, after passing removable checker section 103 is drawn through horizontal checker chamber 114', vertical checker chamber 115 and passes to the stack, the suction for causing this flow being induced by the action of nozzle 111 and throat 112'.

Air for combustion enters at intake pipe 109, is drawn through fan 110, forced through nozzle 111, impinges against damper 116, passes down through chamber 117, vertical checker chamber 115, horizontal checker chamber 114, removable checker section 103, into flue 161, through duct 118 and into the furnace through burners 119. The courses of the air and gases are indicated by arrows.

Dan'lpcrs 126 .rovided at the point of communication of nue 101 with the end of the furnace chamber and similar dampers 120 the positions of which indicated by dotted lines, at the point of communication of flue 101', with the opposite vend of the furnace chamber. Further dampers 121 and 121 aroprovided in ducts 118 andrllS and dempers 122 and 122' in ducts 104 and 1041' In. the operating condition illustrated, dampers 120, 122 and 121 are closed while 120', 122' and 121are fully open. A control 'damper 123- in duct 107 serves to regulate the reiative percentage of gas ley-passed through boiler 1G6and flue-114.; dampers 122 and 122' beingalvvays either fully closed or open. A swinging damper 124 at the junction of duct 107 and header 103 connects this duct alternatively with the one or the other end of header 163.v In each of the intake pipes 109 and`109' two damper-s are provided 125 and 125' and 126 and 126', dampers 126 and 126' for the control of air used for forcing the gases up the stack and dampers 125 and 125 for the control of air for`combus-- In this arrangement including the waste heat boiler, all the advantages of dividing the checkerwork and in the use .of a removable checker section are obtained'for themajor portion of the' gases, while the use of a removable checker sectionin the 'by-passes insures that an unrestricted ilow of comparatively clean gases passes through the waste heat boiler. This system differs from the usual one used with open hearth furnaces, Where it is common practice to pass the whole of the gases through a boiler after they have travelled through the checker chambers, and is particularly suited to the type of furnace Where the air and fuel are introduced through a number of burners in the roof of the furnace. In this type of furnace the gases are at a somewhat higher temperature on leaving the furnace than is usually customarT and there is a greater portion of waste heat available. Particularly is this true Where liquid fuel is employed and the volume of gases per unit of heat developed is considerably less than in the usual ractice. It has bee found that in an ordinary open hearth furnace the gases leave the furnace at a temperature in the neighborhood of 2500 F. while in furnaces equipped with burners in the roof it may be several hundred degrees hotter. Therefore, a portion of the flow is ample for heating the checkerwork. The use of high temperature gases directly in the furnace has the advantage that a small boiler Working under more favorable conditions can be used. lhereas in the ordinary case where all of the gases pass through the boiler after leaving the checker chambers the boiler ordinarily develops about of its rating, with the by-pass arrangement the boiler will develop about 250% of its rated horsepower. The arrangement is particularly suitable also Where for ed draft is employed, owing to the simplicity with which it ts into the system, Whereas with such furnaces the attempt to pass all of the gases through a waste heat boiler after they leave the checker chambers is accomplished i 'n such difficulties that in practice this boiler is often omitted. The gases from the boiler are cooled not only by the boiler itself but by the large admixture of air through the intake pipe and may thus be safely handled by the fan.

In each of the by-pass conduits lO/i and 194' a damper is provided, for reversing the fiovv, but the control of the volume of gas passing through the boiler is secured by a separate damper through which the gases pass regardless of whether they are being drawn at the moment from one end of the furn ce or the other. l)This considerably simplines the managemenJr of the system.

Having thus described my invention what I claim as new and desire to secure by Letters Patent is:

l. In combination with a furnace, a regenerator comprising a number of checker sections one of which is removable and replaceable as a unit and a flue containing said regenerator and connecting With said furnace, said flue being recessed along its bottom and sides for the reception of said removable and replaceable unit.

2. In the regenerative system for a furnace, a flue provided with a transverse opening, a checker section in said ue registering with said opening, a water cooled framework around said checker section constituting with said checker section a structure removable as a unit from said flue, a cover normally sealing said opening, water conduits connected to said water cooled framework passing through said cover, water connections at the ends of said conduits, said cover being removable upon disconnecting said connections Without removal of said checker section.

3. In the regenerative system for a furnace, a nue provided with a transverse opening, a checker section in said flue registering with said opening, a water cooled framework, comprising a plurality of spaced loops of pipe, around said checker system, constituting with said checker section a structure removable as a unit from said flue, a cover normally sealing said opening, a pair of water conduits connected to each loop of said framework, passing through said cover, water connections at the ends of said conduits, said cover being removable upon disconnecting said connectionswithout removal of said checker section.

4, An open hearth furnace, a plurality of burners in the roof of said furnace, a checker section, a flue connecting an end of sait. furnace With said check r section, a Waste heat boiler, a conduit from said flue to said Waste boiler, a checker section in said conduit, said last named checker section being removable as a unit, a checker section in said fine, said last named checker section being removable as a unit.

5. In the regenerative system for a furnace, a discharge vent, a flue connecting said furnace with said discharge vent, a checker section in said iiue, a waste heat boiler, a conduit communicating with waste heat boiler and with said flue at a point between said furnace and said checker section, a fan, a duct connecting said waste heat boiler with the suction port of said and a nozzle in said discharge vent completed to the discharge port of said fan.

6. In the regenerative system for a furnace, a pair of discharge vents, iues connecting the respective ends of said furnace with. said respective discharge vents, checker sections in said flues, a waste heat boiler, by-pass conduits communieating with said waste heat boiler and with .said respective lines at points between said furnace and said checker sections, a fan, associated with each of said discharge vents, a duct connecting said Waste heat boiler with the suction ports of said fans, a nozzle in each of said discharge vents connected to the discharge port of said respective fan, dampers in each of the said by-pass conduits and a damper said duct.

7. .An open hearth furnace, a plurality of burnors in the roof of furnace, a checker chamber, a flue connecting an end of said furnace With said checker chamber, a waste heat boiler, a conduit from said flue to said waste boiler, a checker section in saidconduit, said checker section being removable as a unit.

8. In a furnace regenerative system, a waste gas conduit having a passageway disposed to direct gases in a horizontal f. way disposed to direct gases in a vertical dire"- tion, checker sections in each of said passage- Ways and a dust chamber having means of access thereto intermediate said sections.

9. In the regenerative system for a furnace, a checker section comprising an apertured body of refractory material and an outer metallic frame supporting said material so as to facilitate a vertical manipulation of said section in the plane of said frame.

l0. In a regenerative system for a furnace, a

checker section comprising an apertured body of refractory material, a metal frame having passageways for a cooling medium said frame supporting said material so as to facilitate a vertical manipulation of section in the plane of said frame.

CHARLES E. LEI'IR.

rection; a further passage- CER'IIFICATE GF CORRECTION.

Patent No. i,924,936. August 29, 1933.

CHARLES E. LEHR.

it is hereby certified that error appears in the printed specification ef the afoove numbered patent requiring correction as follows: Page 3, line 104, claim 5, for "completed" read "eonnected"; and that the said Letters Patent should be reati with this correction therein that the same may conform to the record of the ease in the Patent Office.

Signed and sealed this 24th day of October, A. D. 1933,

F. M, Hopkins (Saai) Acting Commissionef ot" Patents. 

